Twitter used to verify whether celebrities' accounts were genuine as a matter of course but gave up after it was overwhelmed with requests to do so.

Ad.ly said executives had been willing to make an exception for @charliesheen, however, as his public meltdown in recent weeks has become one of the most talked-about stories in the US.

Ad.ly CEO Arnie Gullov-Singhtold trade magazine Ad Age: "We know a bunch of people at Twitter, and we reached out to them and told them that probably the biggest name in media right now wants to be on your platform and, of course, they were all right with it... Twitter doesn't verify, but they make exceptions."

Mr Sheen has quickly established his catchphrases on Twitter - the hashtags "#winning" and "#tigerblood".

"Charlie clearly got it, how it worked, what to do. He started doing with some hashtags, like the #tigerblood one, and #winning," said Mr Gullov-Singh.

"Look, he had the number one TV show for a while, he knows how to talk to his fans."

Production of Mr Sheen's top-rated sitcom, Two and a Half Men, was suspended last week after he launched a foul-mouthed attack on its producers. In his Twitter biography, he describes himself as an "unemployed winner".